1. Field of the Invention
The present invention relates to an IEEE 1394-adopted host device and a control method thereof wherein the IEEE stands for the Institute of Electrical and Electronics Engineering.
2. Description of the Related Art
Recently, various kinds of digital devices have been suggested, and the IEEE 1394 standard have drawn attention as a digital interface for constructing a network among these devices. The IEEE 1394 standard particularly has drawn interest because it is recognized as the only specification for the transmission of a HD (High Definition) stream in the field of a digital television.
The IEEE 1394 is a specification of a serial interface which is standardized by the IEEE. The IEEE 1394 was developed as an interface, which connects such devices as a computer peripheral, a video camera, an audio device, a television, a video cassette recorder (VCR), a cable set-top box, an AVHDD (Audio/Video Hard Disk Drive), a DVHS, a video camera, and an MPEG camcorder to a personal computer or a digital television (hereafter, referred as a host device). Three speeds of data transmission are specified, that is, 100 MB, 200 MB, and 400 MB per second. A hot plug-in method is supported to enable direct connections while a host device is operating, and up to 63 slave devices can be connected. Two types of data transmissions, iso-synchronous and asynchronous transmissions, are possible. The iso-synchronous transmission is real-time transmission, so it is suitable for an interface for transferring multi-media information, such as a moving picture or a voice, which requires iso-synchronization, while the asynchronous transmission is a method of dividing and transmitting data so that it can be used for data transmissions between a personal computer and a peripheral like a printer.
On the other hand, in case multiple slave devices are connected to a host device, a user may want to see a list which shows the names of the connected slave devices (hereafter, referred as a device list) through a host device. To provide a device list, however, an additional memory area is conventionally required.
FIG. 1 is a flow chart for explaining a conventional method of displaying a device list of slave devices connected to a host.
First, a user connects one slave device or multiple slave devices to a host device (S10). Then, the host device resets the IEEE 1394 bus (S11). Typically, the reset of an IEEE 1394 bus is performed when a slave device is connected to or disconnected from a host device.
After the reset of the bus, the host device collects device information assigned to each slave device (referred to as device information hereafter) (S12). Examples of device information are the Node ID (Node Identifier), the GUID (Global Unique Identifier), the device type, the model name, and the manufacturer's name. The Node ID changes whenever an IEEE bus is reset, and the GUID is a unique identifier assigned to each slave device.
Then, the host device stores the collected device information, including GUID, in a predefined memory (S13). Generally, an NVRAM (Nonvolatile Random Access Memory) is adopted as a predefined memory.
At this time, device information is stored by applying a predetermined device name to each slave device. For example, STB is applied in case a slave device is a set-top box, and TV is applied to a television, respectively. Then the device information corresponding to the device names is stored.
In case there are at least two slave devices of the same type, a slave device is identified by appending a serial number to the device name. For example, if there are two devices named DVHS, DVHS1 is assigned as one device name and DVHS2 is assigned as the other device name. Hereafter, this process is referred to as a numbering operation.
On the other hand, when a user inputs a display-device-list command into the host device to see a device list of slave devices (S14), the host device retrieves, based on the command, device information stored in a predetermined memory (S15). In this case, device information is retrieved based on the GUID of the connected slave device.
Then, the host device creates and displays a device list using the retrieved device information (S16 and S17).
Examples of the created device list mentioned above are depicted in FIG. 2A and FIG. 2B, respectively. FIG. 2A shows one conventional device list, and FIG. 2B depicts another conventional device list.
As shown in FIG. 2A, STB, DVHS1, DVHS2, and CAMCORDER are displayed in the device list 20. This means that the slave devices connected to the host device are one cable set-top box, two DVHS's, and one MPEG camcorder.
On the other hand, STB, DVHS2, and CAMCORDER are displayed in the device list 30 of FIG. 2B. This means that the slave devices connected to the host device are one cable set-top box, one DVHS, and one MPEG camcorder respectively. In this case, even though there is one DVHS, DVHS2 is displayed in the actual device list. The reason is that the device information of the slave device displays the device name at the time when it was stored in a predetermined memory. That is, the device name at the time when it was stored in a predetermined memory is retrieved through the GUID of a slave device, and the device list is created by use of the retrieved device name. For example, since there were two DVHS's previously, DVHS1 and DVHS2 are displayed in the device list respectively (refer to FIG. 2A), then, in case the slave device registered as DVHS1 is removed from the host device, the slave device stored as DVHS2 still remains as DVHS2 in the storage, so that, when creating a device list hereafter, the slave device stored as DVHS2 is unchanged and displayed as DVHS2. Accordingly, in this case, the device list is displayed inaccurately to a user. That is, such a case confuses a user as to whether the number of DVHS is one or two.
According to a conventional method, a predetermined memory area is required to store device information of slave devices, thereby increasing the unit costs of production.